Detect if device is slow or fast

[Popcorn]

Has anyone experience in detecting if the app is running on a fast or slow device?

My game runs smooth on iPad 2, but slow on iPod 4. What's the best way to deal with this after every possible optimization is done?
I have done so that the game will play equally no matter what the framerate is, so what I want to do is to set fhe framerate to 30 FPS if the device can't handle 60 FPS.
Is this good practice or not adviced? If I do this, is there a good method to detect which device is slow and which is fast enough? Do I have to test for combinations of every model / OS version, or is there a better way?

[Diablohead]

I use the getdevice object to turn off a lot of effects for older devices and it works well, depends on how your game works however.

There is nothing wrong in using 30fps also, right now vsync will force 60 on more powerful devices but a fix is coming.

[Popcorn]

Thanks alot! I'll dive into that object straight away
My game is quite simple, few objects, few effects etc, but there's alot of angle rotation which is what slows the game down. Since that is mandatory for the game, my only option is to set the FPS to 30. That seems to work quite fine though, my only "problem" was to figure out how to set the game to 30 FPS if needed.